Excess urine calcium in patients with idiopathic hypercalciuria (IH) contributes to the formation of calcium oxalate kidney stones. The sources of the excess calcium are intestinal Ca overabsorption and bone resorption. To test the hypothesis that excessive Ca absorption and bone resorption are mediated by an increase in tissue vitamin D receptor (VDR) content, VDR will be measured in dermal fibroblasts from skin biopsy and in peripheral blood monocytes from IH stone-formers, age- and sex-matched non-IH stone formers, and non-stone formers.